Method for making low cost large thin concrete panels in seamless reinforced plastic molds



Nov. 25. 1969 G. J. KREIER, JR

METHOD FOR MAKING LOW COST LARGE THIN CONCRETE PANELS TN SEAMLESS REINFORCED PLASTIC MOLDS Filed NOV. 8, 1968 FICI PREPARE ENGINEERING DRAWINGS AND OPERATION OF SLAB MANUFACTURE KIT FOR PREPARATION OF PRODUCTION MOLDS SHIP TO PRODUCTION SITE CONSTRUCT TEMPORARY MASTER MOLDS EACH MOLD HAVING STRESS BALANCED SUPPORT SURROUNDING SIDES OF THE MASTER MOLD PREPARE SELF PACKING FIBERGLAS- POSITIVE',MAKE MASTER PATTERN AND SHIP TO PRODUCTION SITE POSITIVE PRODUCTION MOLD FACE WITH GEL COAT, SECURE TO A LEVEL BASE AND COAT WHITH A RELEASE AGENT MAKE FIBERGLAS AND GEL COAT PRODUCTION MOLDS FROM MASTER 4 Sheets-Sheet l SHIP MASTERS TO I INSTALL MOLDS ON BASE INSERT WELD PLATES ANO REINFORCEMENT; INSTALL HEATING TUBES, FACILITIES IN EACH PRODUCTION MOLD I ALLOW PANEVL TO CURE REMOVE CURED CONCRETE PANEL WITH VACUUM LIFTER FROM PRODUCTION MOLO SET CONCRETE PANEL IN POSITION ON DWELLING FOUNDATION WELD PLATES TOGETHER TO FORM INTEGRAL DWELLING NEXT PROJECT I N VENTOR GEORGE J-KREIERJR ATTORNEY New. 25, 1969 G. J. KREIER, JR

METHOD FOR MAKING LOW COST LARGE; THIN CONCRETE PANELS IN SEAMLESS REINFORCED PLASTIC MOLDS Filed Nov. 8, 1968 4 Sheets-Sheet FIGZ I FLEXIBLE DRAINAGE CHANNEL FLEXIBLE DRAINAGE CHANNEL R R J o R m I R F. T 0 R TI M x y w A H 7* R O E W. a m m 5 G I o o rru 3/ L M m w H. A H L l L w w I N 13 W 2 n L n r m I I ,H HI O I L Nov. 25, 1969 G. J. KREIER, JR 3,479,786

METHOD FOR MAKING LOW COST LARGE THIN CONCRETE PANELS IN SEAMLESS REINFORCED PLASTIC MOLDS Filed Nov. 8, 1968 4 Sheets-Sheet 3 INVENTOR GEORGE J-KEIER,JF

Nov. 25, 1969 G. J. KREIER, JR 3,479,786

METHOD FOR MAKING LOW COST LARGE THIN CONCRETE PANELS IN SEAMLESS REINFORCED PLASTIC MOLDS Filed Nov. 8, 1968 4 Sheets-Sheet 4 INVENTOR GEORGE J. KREIER,JR

3,479,786 METHOD FOR MAKING LOW COST LARGE THIN CONCRETE PANELS IN SEAMLESS REINFORCED PLASTIC MOLDS George J. Kreier, Jr., 1524 Cambridge St., Philadelphia, Pa. 19130 Continuation-impart of application Ser. No. 590,580, Oct. 31, 1966. This application Nov. 8, 1968, Ser. No. 777,991

Int. Cl. E04]: 1/04; E04c 2/04; E04g 11/00 U.S. Ci. 52745 4 Claims ABSTRACT OF THE DISCLOSURE Method and apparatus for constructing a house or a building from thin, seamless concrete panels in which a unitary fiberglass mold of deeply undercut or wafile pattern is coated with a release agent, concrete is poured therein, leveled, cured and the mold is removed by flexing upwardly so that the cured concrete panel is pulled away for assembling, at the site, a plurality of panels in the building operation.

This is a continuation-in-part application of U.S. patent application Ser. No. 590,580, filed Oct. 31, 1966, now abandoned.

This invention relates to a novel method and to a new, simplified apparatus for making low cost, thin, engineered concrete panels and, more particularly, to a method of making and utilizing improved fiberglass molds for the production of large thin concrete panels as elements of low cost house construction.

A widely used method of constructing low cost houses in the tropical and semi-tropical climate areas of the world is by the utilization of concrete. This material is simple to form and requires a minimum amount of reinforcing material, yet it can provide fireproof and substantially earthquake-proof housing. Concrete is extensively used in underdeveloped countries because of its local availability and low cost and is a fundamental, durable material for meeting the shelter requirements of the people in these countries.

The concrete panels used to form a house are generally made by one of two well-known methods. One method is to construct the pattern molds in situ. Such molds are usually constructed from wood. A separate mold is constructed for each element of the house and is set up in its ultimate position. For example, as shown in Bonet U.S. Patent No. 2,852,931, a mold for a wall is positioned on the foundation at the exact position where the Wall is desired. When the molds are put into position, reinforcing bars are then positioned therein. Concrete is then poured into the mold in what will be its final position and the mold is removed by dismantling after the concrete sets. Obviously, any positioning mistakes are extremely difficult and expensive to rectify.

This first method is uneconomical because the mold must be constructed anew for each house to be built, and quite often the concrete panel formed is damaged in the process of removing the mold therefrom. Concrete must, moreover, be quite heavy in section to permit placement and in order to minimize the damage to the concrete panel during the dismantling of the mold. This thickness is not dictated by economy or ultimate performance of the panel. The materials to build the mold must be transported to the site and a mold for each element of the house must be individually constructed to the exact form, size, shape and position of the final formed concrete panel. Great skill and much supervision is needed, and reuse is poor. The individual mold concept is therefore suitable only for high cost, low production housing connitcd States Patent 0 struction. Mold systems have been devised to improve reuse, but difiiculties in concrete placement remain.

A second known method is precasting, as shown in Midby U.S. Patent No. 2,883,852. In this method, panels are cast in a central production area. Ordinarily, level concrete beds are cast and metal rails are secured along the periphery of the concrete beds. The metal rails must usually be removed and reset for each casting. Reinforcing rods are placed into the mold and concrete is poured therein between the metal rail frame. After the concrete has hardened, the formed panels are removed from the molds and are transported to the ultimate site. At the site, the individual concrete panels are assembled using various standard joints to form the finished house, as is shown in Wilson U.S. Patent No. 2,592,634. The cast concrete panels, including the reinforcing bars, are heavy and bulky, and therefore the cost of transportation from the central casting area to the ultimate assembly site is expensive. Moreover, it is ditficult to remove the panels from the molds of this type of from the metal molds which are also sometimes used. Consequently, the panels must be uneconomically heavy to withstand strains at removal. Such heavy panels are shown in Henderson U.S. Patent No. 2,691,291 and Brauer U.S. Patent No. 2,620,651. Despite attempts made to lighten the weight of the panels, as set forth in Marston U.S. Patent No. 2,139,623, the panels have not been made light enough for widespread, low cost use. Also, in molds of this type, panels cannot be given much detail or finish, partially because of excessive mold cost and partly because more complicated pieces cannot be stripped successfully.

The removal of the cast concrete panels, after curing, from the prefabricated mold is a laborious job requiring the utilization of pinch bars and other similar tools for prying the molds away from the panel or the panel out of the molds. The removal of the panel from the mold is expensive, not only by reason of time and labor involved, but also because of the resultant damage to the mold and the panel, and particularly to the edges thereof. Frequently, the edges of the panels are damaged so extensively that they cannot be used without extensive reconditioning, if at all.

It has been determined that by greatly reducing the size of the concrete panels cast, they can be removed with a reduction of damage; however, this requires the use of additional molds and multiplies the problems of joining the panels together to form a single integral element of the house.

An alternate method for removing the panels from the molds has been the provision of a plurality of orifices in the base of the mold and the forcing of compressed air through the orifices. This method requires the purchase, set-up and transportation of expensive air compressor equipment, and involves the great likelihood that the orifices in the molds base will become clogged with concrete or extraneous matter during shipment or use. This method is obviously uneconomical and not feasible for on-site construction.

Some collapsible and portable molds have been developed from lightweight, disposable material. Their strength is reduced greatly by the wet concrete and the moist condition found in semi-tropical and tropical regions. Additionally, these forms are not reusable and must be discarded after each use, making the cost prohibitive in production.

The present invention eliminates the aforesaid problems by providing a fiberglass master pattern mold from which a plurality of production molds can be constructed. The production molds are provided with a Water-absorbing gel coat and drains for removing rain water. Additionally, the production mold is flexible, thereby allowing a diaphragm action to facilitate the stripping of concrete panels from it. Because of the diaphragm action, the production mold can have substantially vertical walls without any draft. The molds of the prior art, such as shown in Rushing US. Patent No. 2,850,785, do not permit this diaphragm action because of their rigid construction. In accordance with the present invention, the shaping of the horizontal load-bearing structures, the precast large, thin concrete panels made in seamless reinforced plastic molds, requires a wafiie and pan forming technique, as taught in Budd US. Patent No. 2,892,238. The shaping of the vertical panels desirably employs the arcuate reinforcing ribs of Marston U.S. Patent No. 2,139,623.

The above features, plus coating with a release agent, enable a thin extended concrete panel to be cast and removed easily without damage to the mold or to the panel. The molds are light in weight, inexpensive to reproduce, reusable with a minimum amount of reconditioning and cleaning. Great detail can be introduced into the pattern and reproduced economically in production molds, and ultimately without cost in the finished panel.

This invention allows and makes feasible the mass production of low-cost, attractive, fire-resistant, durable houses for families with low income. Low income housing is greatly needed in semi-tropical and tropical regions where adequate housing must furnish protection from hurricane winds, torrential rains and destructive insects. In addition, the houses constructed herefrom have many desirable characteristics for low income families, such as minimum maintenance and maximum durability. The houses can be assembled by unskilled labor quickly and easily by a simple welded operation, followed by grouting and/or sealing the joints.

An object of this invention is to provide a method and apparatus for economically producing large thin concrete panels.

Another object is to provide a master pattern from which a plurality of production molds can be reproduced.

Another object is to provide a master pattern which forms a self-contained shipping container.

Another object is to provide a method and apparatus for removing concrete panels from a mold Without damaging either the mold or the panel.

Another object is to provide a method of assembling precast concrete panels to form a house.

Another object is to provide a method of building low cost houses with unskilled labor.

Another object is to provide means to produce concrete panels having self-contained electrical and mechanical connections.

Another object is to provide a method of making fiberglass reinforced plastic molds.

Another object is to provide a fiberglass reinforced mold having a smooth gel coat surface.

Another object is to provide a gel coat capable of absorbing a percentage of excess water in the poured concrete.

Another object is to provide a method and apparatus for making aesthetically pleasant, highly detailed, smooth finish concrete panels.

Another object is to provide a fiberglass mold that has a flexible diaphragming action to facilitate stripping of concrete panels.

Another object is to provide. a fiberglass mold having drains to facilitate production of the concrete panel outdoors in wet weather.

Another object is to provide a stress balanced mold structure that is seamless.

These and other objects and novel features of the present invention will be more clearly and fully set forth in the following specification, attached drawings and claims. A preferred embodiment of this invention will now be described with particular reference to the accompanying drawings wherein:

FIG. 1 illustrates a flow diagram of the method;

FIG. 2 is a top view of a master pattern;

FIG. 3 is a side cut away view of the master pattern in shipping condition;

FIG. 4 is an enlarged detail view along 44 of FIGS. 3 and 6;

FIG. 5 is a plan view of a production mold;

FIG. 6 is a side cut away view of the production mold;

FIG. 7 is an exaggerated view of the produtcion mold in a flexed diaphragming position;

FIG. 8 is a perspective view of the production mold showing the flex-drain feature; and,

FIG. 9 is an exploded isometric view of a house constructed in accordance with the present invention.

Referring now to the drawings, wherein like reference numbers designate like or corresponding parts throughout the several views, there is shown in FIG. 1 a flow chart illustrating the steps necessary for the mass production of a house in accordance with the present invention.

The first step in the method is the construction of a temporary master mold from which a master pattern will be formed. In order to construct the master pattern, a full scale prototype of the desired production mold is constructed in a manner Well-known to those skilled in the art. While the prototype can be constructed from any of a number of types of materials, such as clay, wood, plaster, plastic, metal or other rigid or resilient materials known and utilized in the art, it is preferred to use plaster of paris applied over a suitable framework. Because the construction of the prototype is a hand operation, the prototype can be made to any form or configuration desired for economic and aesthetic house construction, some common designs being the wafiie or rib slab type, both of which effect a substantial saving in material.

After the full scale prototype mold has been constructed, it is coated with a suitable release agent. A thin uniform layer of a gel coat containing chemically inert hydrophilic fibrous filler and styrene polyester resin is applied over the release agent on the prototype. A fiberglass mat or cloth saturated with conventional catalyzed polyester resin is laid up over the gel coat and residual air bubbles and excess resin are removed from the combination by squeegee or the like to maintain the desired glass fiber content by weight. The number of layers of resin impregnated fiberglass mat and cloth that are built up will depend upon the size of the mold and rigidity and strength desired.

When cured, the fiberglass and gell coat combination will form a rigid positive master pattern conforming to the exact external surface of the prototype. The gel coat and fibergalss laminate is then reinforced with wood stiffeners, a wooden frame around the periphery thereof, and a wooden base. It is finally stripped from the prototype, cleaned and finished,

A complete master pattern 10 is illustrated in FIGS. 2 and 3, which show a typical waffie pattern for the sake of illustration. FIG. 3 shows the master pattern 10 ready to be shipped. A wooden frame 11 is secured along the periphery of the pattern 10 and extends slightly beyond the upper surface and flush with the lowermost surface of the pattern 10. Extending between and secured to opposite sides of the raised portions 12 are wood stiffeners or diaphragms 13. The wood diaphragms 13 impart to the pattern 10 sufiicient rigidity to retain its shape and dimensional accuracy. The lower edge of the frame 11 is secured to a planar base 14, which lies in juxtaposition to the extreme lower surface 15 of the pattern 10. The base 14 extends the complete length of the pattern 10 and is secured to both the frame 11 and the surface 15. While any number of materials can be used for constructing the base 14, wood is preferred because of its low cost and ease of workability. Interconnecting the upper edges of the frame 11 along its entire length are a plurality of slats 16. The slats 16 are raised slightly above the raised portions 12 so as not to come into contact therewith and are positioned in a manner to protect the outer surface of the raised portions 12.

FIG. 4 shows a typical construction of a portion of the master pattern 10 wherein a gel coat 17 provides a smooth seamless surface upon which a production mold 18 will be formed. Underlying the gel coat 17, and integrally bonded thereto, are a plurality of fiberglass layers 19 impregnated with a polyester resin. The fiberglass layers 19 provide a rigid backing for the gel coat 17 while retaining sufiicient resiliency to facilitate the removal of the production mold 18.

The master pattern 10, as illustrated in FIGS. 2 and 3, is in a shipping condition and the frame 11, base 14, and the slats 16 provide a shipping container. Upon receipt at the location where the master pattern 10 will be used, the slats 16 are removed and the frame 11, diaphragms 13 and the base 14 are left intact to provide a rigid yet resilient master pattern.

Master patterns may advantageously be constructed of elements which may be variously arranged to permit a variety of production molds to be produced from a limited number of master elements.

Referring back to FIG. 1, the master pattern 10 is placed horizontally with the gel coat 17 facing upwardly. A thin, uniform coating of a release agent is applied over the gel coat 17, and a thin, uniform layer of gel coat 17 containing chemically inert hydrophilic fibrous filler and styrene polyester resin is applied over the release agent on the master pattern 10. A plurality of glass fiber mats and cloths saturated with conventional catalyzed polyester resin are alternately laid up over the gel coat and residual air bubbles and excess resin are removed from the combination by a squeegee, or the like, to maintain the desired glass fiber content by weight. The number of layers of resin impregnated fiberglass mat and cloth that are built up will depend upon the size of the mold and the rigidity and strength desired. Diaphragms are placed as required to complete the structure.

When cured, the fiberglass and gel coat combination will form a rigid production mold 18 conforming to the exact external surface of the master pattern 10. The master pattern 10 can be used repeatedly for the reproduction of production molds, as desired, in the same manner as hereinbefore described. After a plurality of production molds are reproduced, the master pattern 10 is recrated by securing the slats 16 to the frame 11 and the pattern 10 is shipped to its next destination where additional production molds can be reproduced.

The production mold 18, as illustrated in FIGS. 5 and T 6, is a negative version of the master pattern 10. Extending outwardly along the entire periphery of the production mold 18 is an integral flange 20 which provides a hold-down support when the production mold 18 is in operation. Extending between and secured to opposite sides of a plurality of raised portions 21 are a plurality of wooden diaphragms 13. The wood diaphragms 13 impart to the production mold 18 sufficient rigidity to retain its shape and dimensional accuracy when in production, while enabling it to flex to a limited extent to allow the removal of an extended thin-ribbed planar concrete panel 22, as illustrated in FIG. 7.

Since the production mold 18 is constructed in a substantially identical manner as the master pattern 10, it is obvious that FIG. 4 also shows a typical construction of a portion of the production mold 18.

When the production mold 18 is to be used in producing concrete panels, the mold 18 is set horizontally upon a level surface with the gel coat 17 facing upwardly.

It will be noted by reference to FIGS. 3 and 6 that the internal walls 23 of the master pattern 10 and the production mold 18 are substantially vertical with no appreciable draft. In the present production of concrete slabs, the molds used to form the concrete require a high egree of draft or slope in order to enable the panel to be removed. This, of course, causes many problems, particularly in the construction of multi-storied houses where the panels must abut one another to form a strong, rigid, well-constructed structure. By providing molds having an ability to flex, as illustrated in FIG. 7, the internal Walls 23 can be constructed in a substantially vertical plane in order to form panels having substantially level, straight, parallel edges. As will be described hereinafter, the flexibility of the production mold 18 allows the concrete panels with level edge to be produced without impairing the stripping of the panel from the mold 18.

Another aspect of the present invention is illustrated in FIG. 8, which shows a production mold 18 with a flex-drain in the comer of a mold. Normally, four of these drains occur per panel. In semi-tropical or tropical regions, the amount of rainfall is usually high and showers are frequent. Normally, concrete molds have no provision for draining as they are not ordinarily used outdoors. By providing flex-drains in the corners of the mold 18, water is allowed to drain off while preventing the seepage of concrete through slits 24. Molds are consequently immediately ready to use when the rain stops. The flex-drain has an equally important use in allowing the mold to hinge or flex at the corners of rails to permit the removal of panels with vertical walls.

Referring back to FIG. 1, the production mold 18 is allowed to cure and wood diaphragms 13 are inserted between and secured to opposite sides of the raised portions 21. The diaphragmed mold is then set upon a level horizontal surface with its gel coat 17 facing upwardly. The flange 20 is secured to the level horizontal surface in any one of a number of economical manners, such as wood cleats or concrete rails. The gel coat 17 of the production mold 18 is then coated with a thin, uniform film of release agent. The release agent should be one of the many types of water-insoluble oil materials which tend to float on the Water-wet concrete product. I prefer a treatment with Johnsons Traflic Wax Weekly, with daily application of an emulsion consisting of 10% stearic acid in kerosene.

Before the concrete is poured into the production mold 18, a plurality of reinforcing rods or wire mesh are laid out Within the production mold 18. In addition to the reinforcing material, weld plates, electrical fittings, conduit or cable, and Water pipes are inserted in the mold, and then the concrete is poured therein. In order to insert the weld plates, the production mold 18 may be provided with depressions or reliefs along the walls thereof. By providing depressions in the walls of the mold 18, the weld plates can extend outwardly from the level edges of the concrete panel. The concrete is poured into the mold 18 until it rises slightly above the upper surface of the internal walls 23. It will be noted that the upper surface of the internal walls 23 is horizontal and parallel to the level surface upon which the production mold 18 is secured.

The concrete is distributed and smoothed out until it is level and coplanar With the upper surface of the internal walls 23. Ordinarily, a vibrating screed is guided along the upper surface of the external rails and over the concrete until the concrete settles and fills all the spaces within the production mold 18, thereby eliminating any voids. The low weight and resilience of the mold makes the vibration extremely effective. The smooth surface gel coat facilitates placement.

In addition to imparting a smooth surface to the molded concrete, the gel coat 17 withdraws from the freshly poured concrete a quantity of water up to about 1.5% by weight of the gel coat, thereby facilitating the placing of the concrete and final separation of the concrete from the mold.

After the concrete panel has cured and hardened, a vacuum lifter of the type made and sold by the Vacuum Concrete Corporation of America under the trade name Octopus Lifter is brought into contact with the level planar surface of the concrete panel. The Octopus Lifter has been specified only for illustrative purposes, and it will be obvious that a number of other vacuum lifters can be utilized. The vacuum lifter grasps the level surface of the panel and securely adheres thereto. As the vacuum lifter is raised upwardly, the concrete panel is stripped from the production mold 18. The separation of the concrete panel from the production mold 18 is facilitated by the release agent which is applied to the gel coat and the particular properties of the gel coat, and by the ability of the mold 18 to flex upwardly to a convex configuration, thereby causing the walls 23 to be forced outwardly at an obtuse angle to the horizontal surface upon which the mold 18 is secured. The flexing of the production mold 18 to a convex configuration, as shown in FIG. 7, is assisted by the flex-drains 24 which enable the mold to be flexed at the corners and yet return to its original dimensional configuration subsequent to the stripping of the concrete panel from the mold 18.

It is the combination of the nature of the gel coat and the release agent and the ability of the mold to flex upwardly to a convex configuration that enables the thin concrete panels to be removed easily and efliciently from the mold 18 without damaging either the mold 18 or the panel. Additionally, the ability of the mold 18 to flex outwardly enables the mold to be constructed with substantially vertical walls and eliminates the necessity of providing draft for facilitating the removal of the cast concrete panels. By eliminating the necessity for draft on the walls 23, concrete panels can be cast with smooth level edges which greatly facilitate the setting up of the panels to form a dwelling.

As shown in FIG. 9, a typical housing 25 to be constructed from the concrete panels 22 consists of a roof 26, a floor 27, inner dividing palls 28, a pair of side walls 29, a front wall 30 and a rear wall 31. It will be noted from FIG. 9 that side walls 29 are substantially identical, that front wall 30 and rear wall 31 are also substantially identical, and that all the walls are of one piece construction. The roof 26 and the floor 27 are of substantially identical construction and consist of two separate panels joined together along a longitudinal edge. While the roof 26 and the floor 27 are shown as being constructed from two separate panels, it will be obvious that, because of the present novel method of manufacting thin, seamless panels 22, the roof 26 and the floor 27 can be constructed from one integral panel.

In operation, only three master molds are necessary for the complete external construction of the house 25. One master mold 10 is necessary for the roof 26 and the floor 27, another master mold 10 is necessary for the side walls 29 and another for the front wall 30 and the rear wall 31. Each master mold 10 provides a pattern from which a plurality of the production molds 18 can be reproduced as described hereinbefore. In order to provide a solid foundation upon which to build the house 25, a plurality of piles 32 are placed into the ground. The use of the piles 32 is highly desirable where the ground upon which the house 25 is to be built is incapable of securely supporting the house or where the terrain is irregular. After the piles 32 are set into the ground the floor panels 27 are placed in a horizontal position on top of the piles by a vacuum lifter. The floor panels 27 are then secured to the piles 32 in any well-known manner, such as welding or adhesive connections.

In constructing the front, rear and side walls, those portions of the walls which comprise windows 33 are removed. In order to cast walls with openings to provide windows 33 and doors, the production mold 18 is provided with a plurality of extended raised portions (not shown). The extended raised portions are similar to the raised portions 21 as illustrated in FIG. 8, but extend upwardly beyond portions 21 to a level flush with the upper surface of the internal walls 23. Therefore, when concrete is poured into the mold 18 and compacted to a plane flush with the upper surface of the internal walls 23, the extended raised portions will provide a plurality of openings 33 in the panel 22.

The front, rear and side walls are placed on the floor panel 27 by the vacuum lifter and the weld plates of adjacent abutting panels are welded together and to the floor panel 27. After the walls 29, 30 and 31 are secured to each other and to the floor 27, the inner dividing walls 28 are positioned and secured within the inner portion of the house 25 as defined by the floor 27, the side walls 29, the front wall 30 and the rear wall 31.

After the inner dividing walls 28 are in position, the roof panels 26 are lifted and placed upon the upper edges of the walls 28, 29, 30 and 31 by a vacuum lifter. The roof 26 is positioned upon the walls in a substantially horizontal position and is secured to the walls. When the roof 26 is cast in two sections, the sections are placed in abutting relationship along their longitudinal edges. The dividing line between the two roof panels 26 is coaxial with the center line of an inner wall 28 and the roof panels 26 are partially supported thereby.

While for the sake of illustration a single story house has been described, it will be obvious that any number of stories can be constructed and the roof of the bottom story will serve as the floor of the upper story. Because of the substantially smooth level edges of the panels 22, the walls 28, 29, 30 and 31 are easily secured to the roof 26 and the floor 27 in a perpendicular manner. The method of securing the walls to the floor, to the roof and to one another can be by welding or cementing, or by any other manner well-known in the art.

After the complete house 25 has been constructed, the connection joints between the various panels are filled with an insulating material which is capable of allowing expansion and contraction. While a number of commercially available insulating materials can be used, it is preferred but not necessary that a flexible insulating material, such as that produced by Expandite Ltd. of England and sold under the trade name of Thioflex, be used.

The production mold which is illustrated in FIGS. 5, 6 and 8 is unusually resistant to wear by erosion from the hardened cast concrete because of the high tensile strength high hardness, toughness and resistance to alkaline chemicals in the concrete. The limited flexing distortion of the central areas of the production mold would ordinarily be expected to wear away and crack the inner, deepdrawn and deeply undercut plastic surfaces of the mold and would further be expected to abrade the inner extended surfaces of the mold.

Surprisingly, these mechanical deficiencies are not encountered in the deep-drawn undercut waflleboard production mold of FIGS. 5, 6 and 8. The use of the hydrophilic fibrous filler lining of gel coat 17 as described in relation to FIG. 1 is set out in my earlier patents, U.S.P. 3,317,178 and U.S.P. 3,295,818, which describe the reinforcing effect at the inner layers provided by the woven glass fabric and improved parting effect provided by the hydrophilic liner when conventional hydrophilic mold release agents are employed, such as kerosene, mineral oil, wax in oil, fatty acid in kerosene or in oil, and the like.

I am aware that wafile or multi-compartmented molds have been used for casting concrete panels or blocks. An example of such a prior art mold is shown in Ratclifie US. Patent No. 2,867,887 in which the ends of the mold are dismantled and the dismantled mold is inverted in order to release the hardened concrete blocks or panels which are formed. This type of mold, consisting of a plurality of joined compartments, differs from a mold which consists of a single unitary surface as used in the method of the present invention, since the latter is capable of producing thin, seamless concrete panels which have level edges from which the mold is removed by limited flexing and which need not be inverted for mold removal. It is surprising that there is no sag in the present mold since sag occurs in the plurality of joined compartments due to the weight of the blocks during the molding operation in Ratcliife. The utilization of the Ratclifie mold in assembling slabs to form a house as in Wilson US. Patent No. 2,592,634 would not produce a practical and efiicient building method quite apart from the disadvantages of the requirement for reinforcing bars during assembly, which is prohibitively costly, and the great difficulties encountered in the transportation of the broad wafile pans which have been set out in the sixth paragraph of the present application.

The absence of level edges, the uneven cross section due to the sag of the middle compartments of Ratclifie and the undesirable appearance of the seams which are inherently produced by the Ratclitfe molds cause sufiicient distortion in the concrete panels to prevent the joining of these panels in wall structures under the close tolerances required for successful commercial operation.

Flexible plastic receptacles which mold soft comestibles such as described in Tupper US. Patent No. 2,955,- 044 have never been successfully employed for the molding of concrete. The membranous shape-sustaining receptacles can be manipulated by simple finger pressure and given reverse bends of 90, the thickness of the membrane being such that it could not hold the concrete load for the undercut panel without being supported at each compartment or undercut portion.

Therefore, it is apparent that the present method of construction employs unique thin seamless concrete panels of waffie section by a novel combination of steps in which the production mold is positioned at the site, the concrete is poured and leveled and thereafter cured, and the mold is removed by simple flexing in a unique manner without the usual dismantling, the assembly of the panels proceeding at the site where the house is being constructed.

It will be obvious to those skilled in the art that, while a preferred embodiment has been described in detail, modifications may be made without departing from the spirit and scope of the invention as defined in the claims which follow.

I claim:

1. A method of constructing a house therefrom, comprising the steps of:

positioning a flexible, integral, stress balanced, patterned, fiberglass mold having drain slits extending along at least one vertical edge upon a level surface in a manner such that said mold edges are level and on a common horizontal plane;

securing a pair of outer opposite edges of said flexible fiberglass mold to said level surface;

coating said flexible fiberglass mold with a release agent;

positioning utility connections in said coated mold;

pouring concrete into said mold;

compacting said concrete within said mold wherein said concrete comes into abutment with the coated vertical walls of said mold;

leveling said concrete wherein the upper surface of said concrete is coplanar with the mold edges; curing said concrete to form a patterned panel having level edges perpendicular to said upper surface; inverting said mold and concrete;

flexing said mold upwardly to a convex configuration wherein said vertical outer edges of said mold assume an acute angle relative to said level edges of said cured panel;

removing said cured concrete panel from said flexed integral mold without dismantling or removing said mold from its secured position;

transporting said concrete panel to a site where said house will be constructed;

positioning said panel in its ultimate position, whereby said level edges permit the perpendicular orientation of the panels relative to each other; and securing said concrete panel to adjacent panels.

2. A method in accordance with claim 1 wherein the steps of flexing said mold outwardly to a convex configuration and removing said panel from said mold is accomplished with a vacuum lifter.

3. A method in accordance with claim 1 wherein a plurality of reinforcing members are positioned in said mold prior to the pouring of concrete therein.

4. A method in accordance with claim 1 wherein said mold has a plurality of extended raised portions for forming openings in said panels.

References Cited UNITED STATES PATENTS 1,796,048 3/1931 Robinson 52-281 2,078,144 4/1937 Kenan 52-602 2,111,577 3/1938 Thomas 52-602 2,306,548 12/1942 Leemhuis 249- 2,316,752 4/1943 Atkinson 249-415 2,455,650 12/1948 Billner 52 745 2,592,634 4/1952 Wilson 52-22o 2,867,887 1/1959 Ratcliffe 249-127 2,955,044 10/1960 Tupper 249-127 3,295,818 1/1967 Kreier 249-134 3,317,178 5/1967 Kreier 249-415 FRANK L. ABBOTT, Primary Examiner J. L. RIDGILL, JR., Assistant Examiner US. Cl. X.R. 

